Type 2 diabetes is an increasingly prevalent disease that due to a high frequency of complications leads to a significant reduction of life expectancy. Because of diabetes-associated microvascular complications, type 2 diabetes is currently the most frequent cause of adult-onset loss of vision, renal failure, and amputations in the industrialized world. In addition, the presence of type 2 diabetes is associated with a two to five fold increase in cardiovascular disease risk.
After long duration of disease, most patients with type 2 diabetes will eventually fail on oral therapy and become insulin dependent with the necessity for daily injections and multiple daily glucose measurements.
The UKPDS (United Kingdom Prospective Diabetes Study) demonstrated that intensive treatment with metformin, sulfonylureas or insulin resulted in only a limited improvement of glycemic control (difference in HbA1c ˜0.9%). In addition, even in patients within the intensive treatment arm glycemic control deteriorated significantly over time and this was attributed to deterioration of β-cell function. Importantly, intensive treatment was not associated with a significant reduction in macrovascular complications, i.e. cardiovascular events. Therefore many patients with type 2 diabetes remain inadequately treated, partly because of limitations in long term efficacy, tolerability and dosing inconvenience of existing antihyperglycemic therapies.
Oral and non-oral antidiabetic drugs conventionally used in therapy (such as e.g. first- or second-line, and/or mono- or (initial or add-on) combination therapy) include, without being restricted thereto, metformin, sulphonylureas, thiazolidinediones, glinides, α-glucosidase inhibitors, GLP-1 or GLP-1 analogues, and insulin or insulin analogues.
The high incidence of therapeutic failure is a major contributor to the high rate of long-term hyperglycemia-associated complications or chronic damages (including micro- and makrovascular complications such as e.g. diabetic nephrophathy, retinopathy or neuropathy, or cardiovascular complications) in patients with type 2 diabetes.
Genetic association studies have identified genetic variations in several genes which are associated with increased risk of type 2 diabetes mellitus. E.g. variations in the genes TCF7L2, KCNJ11 and PPARG independently and interactively increase the risk of progression from impaired fasting glucose and impaired glucose tolerance to overt diabetes. While variation in KCNJ11 may alter insulin secretion and variation in PPARG may alter insulin action, TCF7L2 (transcription factor 7-like 2) is the major susceptibility gene identified to date for type 2 diabetes in various ethnic groups (e.g. Europeans, Indian and Japanese people, Mexican Americans and West Africans). Polymorphisms (single nucleotide polymorphisms, so called SNPs) in TCF7L2, such as e.g. rs12255372 and, particularly, rs7903146, are strongly associated with diabetes. The risk of developing type 2 diabetes is increased by roughly 45% (Odds ratio 1.45) among carriers of one risk T-allele of TCF7L2 rs7903146 (CT heterozygotes), and is at least doubled (Odds ratio of 2.41) among TT homozygotes compared to CC homozygotes wild genotypes (Grant et al, Nature Genetics, Vol. 38, 2006, p 320-323). TCF7L2 risk genotypes are associated with increased TCF7L2 expression in pancreatic beta cells, impaired (glucose-stimulated) insulin secretion, incretin effects and enhanced rate of hepatic glucose production as well as predisposition to and prediction of future type 2 diabetes (cf. Lyssenko et al., The Journal of Clinical Investigation, Vol. 117, No 8, 2007, p. 2155-2163). There is evidence that the TCF7L2 rs7903146 risk variants are associated with lower incretin effect on insulin secretion, which may be based, at least in parts, on an impaired sensitivity of the beta cells to incretins.
Thus, diabetes patients harboring TCF7L2 risk variants, particularly carriers of the at risk T-allele of TCF7L2 rs7903146, such as patients harboring the TCF7L2 rs7903146 CT genotype or, particularly, patients harboring the TCF7L2 rs7903146 TT genotype, are expected to be difficult to treat in antidiabetic therapy.
Therefore, there is an unmet medical need for methods, medicaments and pharmaceutical compositions or combinations with a good efficacy with regard to glycemic control, with regard to disease-modifying properties and with regard to reduction of cardiovascular morbidity and mortality while at the same time showing an improved safety profile.
DPP-4 inhibitors represent another novel class of agents that are being developed for the treatment or improvement in glycemic control in patients with type 2 diabetes.
For example, DPP-4 inhibitors and their uses are disclosed in WO 2002/068420, WO 2004/018467, WO 2004/018468, WO 2004/018469, WO 2004/041820, WO 2004/046148, WO 2005/051950, WO 2005/082906, WO 2005/063750, WO 2005/085246, WO 2006/027204, WO 2006/029769, WO2007/014886; WO 2004/050658, WO 2004/111051, WO 2005/058901, WO 2005/097798; WO 2006/068163, WO 2007/071738, WO 2008/017670; WO 2007/128721, WO 2007/128724, WO 2007/128761, or WO 2009/121945.